What Is LPF On An Amp?

By Richard Pryn •  Updated: 04/27/22 •  6 min read

If you have recently bought an amp, or only just taken notice of all the different knobs and buttons on it, then there is potentially a whole world of settings out there for you to explore.

Many of these are initialized into LPF or HPF and other initialisms. So they can warrant some explanation.

What Is LPF On An Amp

Most of the time the settings on the amp are pretty basic and simple to understand once you get past the jargon. The great thing about an amp is that you can play around with and use each setting with ease.

Although when you don’t understand how they function you may not understand their effects.

In this article we will explain what LPF, and its counter-function HPF, mean as well as some other common amp settings.

What Does LPF Mean?

LPF simply means low pass filter, this is a common filter used all the time across music and music production, perhaps most notably on turntables.

In essence, all a low pass filter does is filter out the high frequencies while ‘passing’ the low frequencies. It is essentially a filter that affects the high frequencies but not the low.

It is an easy way to mix out the vocals of a song when mixing, or when mastering it can help with key changes and other things.

In terms of your amp, this basically just means that the higher frequencies will be affected by a filter, whereas the low frequencies will still pass through. The higher notes will be quieter while the lower notes will be louder.

This is more of an effect than anything else, LPF usually serves a more practical function of reducing hissing noises or other high frequencies that may have occurred on a recorded track.

It can be useful on an amp to get rid of the higher frequencies that are annoying.

What Is A HPF?

A HPF operates the same way as an LPF but is counter-functional.

In other words, a high pass filter will filter the lower frequencies of a song while the high frequencies will remain unchanged. Most often this will affect the bass.

There is more variability in terms of what classes as a high frequency, vocals, guitar, etc. can all be high, but low frequencies are almost solely bass.

This will affect the low end of your amp, anything on the three low strings will be ‘filtered’ and just sound quieter, or have its low end become more muted. The high notes will remain unaffected.

This is a common method for DJs to swap the bass on two different tracks, by enacting a HPF on one.

If you find that your bass has become quite grumbly or shay or even distorted, a HPF can really help iron out the low end.

Moreover, it can just apply a muted sort of feel to the song and act more as an effect than anything else. A high HPF can make the song sound like it’s playing in the other room.

Other Common Settings

There are many settings an amplifier may have, all of which have independent and separate functions, we have tried to cover some of the most common.

Distortion

An amplifier can have a distortion circuit built into it. Distortion is a very popular feature on amplifiers because it gives them a unique sound. Distortion, as the name suggests, distorts the signal coming out of the amplifier.

The problem with distortion though is that it can cause feedback problems if it is too strong. Distortion is a common effect used in rock music.

Reverb

Reverb is another setting that is commonly found on amps. Reverb simulates the natural reverb in a room. It is a great tool to add depth to a recording, especially if you’re using headphones.

Reverb essentially makes the signal a little longer but also trailing off.

Reverb is a bit like chorus, it essentially makes the audio sound like it is being played in a gran hall or something similarly acoustic.

What Is LPF On An Amp (1)

Chorus

Chorus is similar to reverb but a little less effected. A chorus is essentially just the audio being followed by a mildly quieter reproduction of the audio with a mild delay.

It makes the audio sound as if it was being played a million times at once, but in a good way.

Gain

Gain is perhaps the most commonly used dial on the amp. Gain controls how loud the output from the speaker is. If you turn up the gain then the volume gets louder, if you turn down the gain then the volume goes down.

The way that volume and gain are different is that the gain essentially controls the strength of the sound wave and frequencies, while volume just increases decibels, essentially.

Final Thoughts

As you can see there are many different knobs and dials you can play with on an amp. The more money you pay for an amp, you will generally get more dials and more effects and features.

Some of the most basic amps like a mono amp will basically only have a volume and gain function. While the higher end gear can have many, many more.

In all honesty, any description you receive of these effects will either be so bogged down in the theory and function of them, how it affects the waveforms, compression, etc., that you won’t have a clue what it does, or the description simply can’t do it justice with words.

Sometimes if you want to learn about these things the best option is to simply give them a go and try them out, you will get a much better understanding of what the effects are and how they operate by using them than by trying to understand someone’s explanation of them.

We hope these explanations have ironed out the issues you were having, or at least give you some confidence to use these effects and experiment with them! There’s no right way to go about this so just get experimenting.

Richard Pryn

Hey there. I am an award winning composer for movie trailers, including Bladerunner 2049, Diablo II, WandaVision, and loads more. I am the founder of The Trailer Music School where my aim is to teach everything I know about music composition, production, and generally being a functional human being. I podcast, blog, vlog and jog (sometimes). I also love coffee, nachos and self-improvement. I live with my wife, three kids and numerous pets. I am also known by my pseudonym, Richard Schrieber (it’s a long story).

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